In a conventional electronic circuit device for a compressor, a printing circuit board on which an electronic component such as a semiconductor element is mounted is put into a storage box from an opening part of the storage box, and the opening part is closed with a lid. A fixing structure of the printed circuit board in the conventional electronic circuit device for the compressor is explained, for example, by referring to an electronic circuit device for a compressor disclosed in Unexamined Japanese Patent Application Publication No. 11-317570 (patent document 1).
FIG. 8 is a perspective exploded view of the conventional electronic circuit device for the compressor disclosed in patent document 1. In FIG. 8, storage box 100 is composed by injection molding of nylon, ABS resin, or other synthetic resin. Storage box 100 has opening part 108 in a size slightly larger than printed circuit board 104 for accommodating printed circuit board 104 in its inside.
On printed circuit board 104, semiconductor element 112 for driving the compressor is mounted. To reduce the temperature, heat sink 116 formed of a metal of smooth heat conduction is tightly adhered to semiconductor element 112. Connector 120 is connected to printed circuit board 104.
Storage box 100 is opened at a position facing connector 120 when printed circuit board 104 is accommodated, and cord lead-out part 124 is formed. Hole parts 128 are formed at four corners of printed circuit board 104. Printed circuit board 104 is fixed to screw receiving parts 137 provided at four positions in a bottom part of storage box 100, by means of circuit board fixing screws 132 by making use of hole parts 128. At four corners around opening part 108 of storage box 100, mounting holes 136 are provided. Holes 142 are provided at four corners of lid 140. Lid 140 is fixed to storage box 100 by lid fixing screws 146 by making use of holes 142 and mounting holes 136, and closes opening part 108 of storage box 100.
In the conventional electronic circuit device for the compressor having such configuration, its assembling process is explained below. First, printed circuit board 104 is inserted from opening part 108 of storage box 100. Printed circuit board 104 is tightened in a plate thickness direction by circuit board fixing screws 132 in all of four hole parts 128, and is fixed to the bottom part of storage box 100. Lid 104 fixed so as to close opening part 108 of storage box 100 by means of lid fixing screws 146 by using four holes 142 and mounting holes 136. As a result, printed circuit board 104 is covered by storage box 100 and lid 140. Thus, the electronic circuit device for the compressor is assembled. Connector 120 is provided at a position facing cord lead-out part 124. Therefore, cords (not shown) for communicating with outside of the electronic circuit device for the compressor are connected by way of cord lead-out part 124.
When power is supplied to the electronic circuit device for the compressor, semiconductor element 112 is heated. Semiconductor element 112 is provided with heat sink 116, and the heat of semiconductor element 112 is released by way of heat sink 116.
In the conventional configuration, however, the heat from semiconductor element 112 transmitted to heat sink 116 is not release to the air outside of storage box 100. Accordingly, the heat of semiconductor element 112 for driving the compressor stays inside of storage box 100, and the heat is not released sufficiently. As a result, the temperature of semiconductor element 112 elevates, and the reliability of semiconductor element 112 is lowered.
Besides, along with temperature changes in the inside of storage box 100, due to difference in the coefficient of linear expansion between printed circuit board 104 and storage box 100, a stress is applied to four hole parts 128 for fixing printing circuit board 104. As a result, printed circuit board 104 may be broken.